Project Summary: Deficits of white matter and myelin have been implicated in several neuropsychiatric conditions such as schizophrenia, depression, and bipolar disorder. The cause of hypomyelination in these disorders is not well understood and may contribute to the patients? clinical symptoms; therefore, there is a therapeutic need for medications which adjust the levels of myelin in adults. Additionally, discovering more targets which enhance oligodendrocyte formation, may illuminate novel aspects to the underlying biology of oligodendrocyte formation. Oligodendrocyte progenitor cells (OPCs) differentiate into oligodendrocytes for myelination of axons throughout the CNS in both the developing and developed human brain. Recently, it was reported that there is a differentiation defect in OPCs obtained from patients with schizophrenia. To discover novel therapeutics which enhance formation of oligodendrocytes from OPCs, we and others performed in vitro chemical-genetic screens. These screens served to illuminate that inhibition of the cholesterol biosynthesis pathway at specific steps is a dominant mechanism for enhanced oligodendrocyte formation. This work aims to further parse the importance of specific enzymes and their sterol substrates in this pathway in enhancement of oligodendrocyte formation and to determine the efficacy of these small-molecules in mouse and human OPCs. In aims 1i and 2i we systematically interrogate the cholesterol biosynthesis pathway and characterize the effects of knockdown of sterol-14 reductase and enzymes C4-demethylation complex on enhance oligodendrocyte formation and on the sterol pathway. In aims 1ii and 2ii we determine the effects of treating cells with the sterol substrates for these enzymes on oligodendrocyte differentiation and the sterol pathway. Lastly, in aim 3 we determine the lipid and phenotypic effects of these small molecules on human OPCs. This proposal will lead to a greater understanding of the role of the cholesterol biosynthesis pathway in OPC differentiation and oligodendrocyte formation.